Decomposable organic waste is often buried in landfill sites. "Organic waste" for purpose of this specification is essentially animal and vegetable matter. Spoiled produce and meat products from large grocery chins, table scraps from restaurants, the contents of grease traps in food processing plants and restaurants, and fat and animal by-products from packing houses are typical sources of such organic waste. In a landfill site, soil microorganisms are expected to decompose the waste. However, lack of oxygen to subsurface soil and lack of appropriate nutrients to support decomposition result in very poor break-down of the waste. Even simple vegetable matter devoid of fats and oils may be preserved for decades.
Disposal of oil-containing organic waste remains a particularly acute problem. The term "oil-containing" as used in this specification should be understood as materials containing "fat, oil and grease" as those terms are currently used in the waste disposal industry or combinations of such materials. It also encompasses organic materials such as mineral oil. All such oil-containing materials are essentially fats or oils, ultimately of vegetable or animal origin, which are decomposable by soil organisms.
Many cities have begun to halt or severely restrict dumping of oil-containing organic waste in land-fill sites. The products of decomposition pose a potential threat to groundwater, which continues for many years owing to slow decomposition rates. In state-of-the-art landfill sites, where leachate is collected to avoid contamination of groundwater, the products of decomposition are commonly processed at water treatment facilities, which entails additional cost. One approach permitted in landfill sites involves entombment of such wastes. The waste is incorporated into other materials that form solid permanent bodies, avoiding potential groundwater contamination. Entombment processes are costly, and incineration is a principal alternative.
Direct application of oil-containing waste to surface soil has not been permitted in many jurisdictions. Although soil microorganisms can potentially decompose fats and oils, soil conditions are usually inappropriate for effective and rapid decomposition. The waste materials tend to linger, attracting insects and rodents. The lingering fats and oils also tend to alter the physical properties of the soil, interfering with absorption and distribution of water, which can deleteriously affect growth of a crop in a subsequent season.
Oil-containing waste might be applied to surface soil and rapidly decomposed with appropriate nutrients. Such waste typically has a high carbon content, but comparatively little nitrogen and phosphorus to support decomposition of the carbon by soil organisms. Nitrogen and phosphorus might be applied to the soil in sufficient quantities to induce rapid decomposition. The prior art does not appear to have pursued such an approach. Large quantities of nitrogen and phosphorus are required, making the approach costly. The large quantities of nitrogen and phosphorus also create a very serious risk of groundwater contamination.
It would thus be desirable to provide a process for disposal of organic waste, particularly oil-containing waste, which, unlike prior processes, does not pose an environmental threat, is cost-effective, and results in a benefit beyond mere disposal of waste.